1638189197 has 2 divisors, whose sum is σ = 1638189198. Its totient is φ = 1638189196.

The previous prime is 1638189187. The next prime is 1638189233. The reversal of 1638189197 is 7919818361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1638144676 + 44521 = 40474^2 + 211^2 .

It is a cyclic number.

It is not a de Polignac number, because 1638189197 - 2⁴ = 1638189181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1638189107) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 819094598 + 819094599.

It is an arithmetic number, because the mean of its divisors is an integer number (819094599).

Almost surely, 2^1638189197 is an apocalyptic number.

It is an amenable number.

1638189197 is a deficient number, since it is larger than the sum of its proper divisors (1).

1638189197 is an equidigital number, since it uses as much as digits as its factorization.

1638189197 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 53.

The square root of 1638189197 is about 40474.5499913217. The cubic root of 1638189197 is about 1178.8395171820.

The spelling of 1638189197 in words is "one billion, six hundred thirty-eight million, one hundred eighty-nine thousand, one hundred ninety-seven".